Quorum requirements for a referendum to be valid

Articles 79 and 96 ofthe Constitution do not specify a turnout or approval quorum.

Constitution ofJapan

(Cameinto effect May 3, 1947; not amended since)

http://www.kantei.go.jp/foreign/constitution_and_government_of_japan/constitution_e.html

Article 79

(1) TheSupreme Court shall consist of a Chief Judge and such number of judges as maybe determined by law; all such judges excepting the Chief Judge shall beappointed by the Cabinet.
(2) The appointment of the judges of the Supreme Court shall be reviewed by thepeople at the first general election of members of the House of Representativesfollowing their appointment, and shall be reviewed again at the first generalelection of members of the House of Representatives after a lapse of ten (10)years, and in the same manner thereafter.

(3) In casesmentioned in the foregoing paragraph, when the majority of the voters favorsthe dismissal of a judge, he shall be dismissed.

(4) Matterspertaining to review shall be prescribed by law.

(5) The judges ofthe Supreme Court shall be retired upon the attainment of the age as fixed bylaw.

(6) All such judgesshall receive, at regular stated intervals, adequate compensation which shallnot be decreased during their terms of office.

Article 96

(1)  Amendments to this Constitution shall beinitiated by the Diet, through a concurring vote of two-thirds or more of allthe members of each House and shall thereupon be submitted to the people forratification, which shall require the affirmative vote of a majority of allvotes cast thereon, at a special referendum or at such election as the Dietshall specify.